Neurons of origin and fiber trajectory of amygdalofugal projections to the medial preoptic area in syrian hamsters

Abstract

The amygdaloid neurons of origin and the trajectory of amygdaloid fibers to the medial preoptic area of the adult male Syrian hamster were identified by using horseradish peroxidase (HRP) histochemistry. After iontophoresis of HRP into the medial preoptic area, retrogradely labeled amygdaloid neurons were located in the dorsal and caudal parts of the medial amygdaloid nucleus and throughout the amygdalohippocampal area. No amygdaloid neurons were labeled after HRP applications confined to the most rostral portion of the medial preoptic area (anterior to the body of the anterior commissure). Following more caudal medial preoptic area injections (body of the anterior commissure to the suprachiasmatic nucleus) the distribution of retrogradely labeled cells in the medial amygdaloid nucleus and the amygdalohippocampal area revealed no topographic organization of the amygdalopreoptic connections. When amygdaloid neurons were labeled, the amygdalohippocampal area contained two to five times as many HRP-filled cells as the medial amygdaloid nucleus. Retrogradely transported HRP could be followed from the medial preoptic area to the amygdala through fibers in the dorsomedial quadrant of the stria terminalis. In addition, electrolytic lesions of the stria terminalis prior to iontophoresis of HRP into the medial preoptic area prevented retrograde transport to neurons in both the dorsocaudal medial amygdaloid nucleus and the amygdalohippocampal area. These results confirm earlier observations describing the location of autoradiographically labeled efferents from the medial amygdaloid nucleus to the medial preoptic area and provide new information about the restricted region within the medial amygdaloid nucleus from which these projections arise. They also suggest that, unlike the projections from the medial amygdaloid nucleus to the bed nucleus of the stria terminalis, the efferents to the medial preoptic area travel entirely in the stria terminalis.

Projections of the posterodorsal preoptic nucleus and the lateral part of the posterodorsal medial amygdala in male gerbils, with emphasis on cells activated with ejaculation

“…In rats, the area lateral to the medial MPN (i.e, the lateral MPN) was labeled much less than the medial MPN after Pha-L injections that filled the MeApd (Canteras et al, 1995). Projections to the PdPN were not mentioned in studies of MeApd outputs in rats or hamsters but are suggested by the density of labeled fibers shown in the POA (Gomez and Newman, 1992;Canteras et al, 1995;Coolen and Wood, 1998) just rostral and caudal to where the PdPN is located (Maragos et al, 1989;Swanson, 1992) after tracer injections in the MeApd.…”

Altered gating of opiate receptor-modulated K + channels on amygdala neurons of morphine-dependent rats

“…In preliminary studies, channel responses to opioids were not observed on the smaller cells (not shown), and so only the larger cells were used here. The AHA is known to be a densely packed cell layer made up of 30-to 40-m pyramidal or spindle-shaped projection neurons, whereas the other regions of the amygdala that are directly ventral to the AHA and thus are also included in our preparation comprise smaller neurons and glia (17). Consequently, we recorded principally from AHA projection neurons.…”

Inheritance of steroid-independent male sexual behavior in male offspring of B6D2F1 mice

“…The medial amygdala receives projections from the main and accessory olfactory bulbs (Davis et al, 1978; Lehman and Winans, 1982), and sends its projections to the mPOA and bed nucleus of the stria terminalis (Gomez and Newman, 1992; Kevetter and Winans, 1981; Maragos et al, 1989). B6D2F1 hybrid maters retain the ability to discriminate between female and male mice while non-maters have lost this ability (Park et al, 2009), and this finding further supports the hypothesis that the neural circuitry connecting the MPOA to the olfactory system that governs male sexual behavior may remain intact in the maters but not in the non-maters.…”